In the 1970s–1980s, medium- and high-vinyl-content polybutadiene (Intolene-50, 80 and Nipol BR1240, Nipol BR1245) have been developed and produced with alkyl lithium catalyst firstly by International Synthetic Rubber Co., Ltd, England and Japanese Geon Co., Japan respectively. Said kind of rubber features in low heat-generating, good wet-skid resistance, low resistance to rolling, good compatibility with natural rubber, etc. A Co series catalyst was developed by Japanese Synthetic Rubber Co. and was used to produce a syndiotactic 1,2-polybutadiene thermoplastic elastomer with low crystallinity in the year of 1974. There were many research reports on Mo, Ti, Cr, Fe-based complex catalyst. Simultaneously, the research including pilot scale experiments for synthesizing vinyl polybutadiene rubber by Li, Mo and Fe-based catalyst and the applied research on trial product had been carried out in China, but so far the vinyl polybutadiene rubber has not been manufactured commercially in China yet.
The advantages of organolithium catalyst system for manufacturing vinyl polybutadiene are as follows: on the one hand, said catalyst system is capable of controlling, effectively and over a wide range, the process structure (microstructure, continuous structure (block, randomness), geometric structure (linear, branched, star-shaped), long-range structure (molecular weight); on the other hand, said catalyst system is capable of manufacturing a variety of branded goods by changing the additive and solvent in a set of equipments. Although the Li catalyst can be used to produce polybutadiene rubbers having different vinyl contents, the Li catalyst is in need of polar solvents, for example, ethers, amines and sulfides, more specifically, such as tetrahydrofuran, diethylene glycol dimethyl ether, tetramethylethylenediamine and the like. Consequently, the synthetic cost is increased and the polymeric system-purifying and solvent-refining become more difficult. Meanwhile, since the vinyl content is inversely proportional to the polymerization temperature, i.e. the vinyl content decreases with the increase of temperature in the presence of the polar solvent. A lower polymerization temperature is harmful to energy-saving, especially to long chain-branching and molecular weight distribution (hereinafter referred to as MWD)-broadening. In order to obtain a definite degree of branching, a coupling reaction is often carried out by adding a multifunctional compound such as titanium tetrachloride, diesters and the like. By pulsafeeding the catalyst in batches, the MWD of the polymer is broadened and the processability is improved. By the Mo catalyst, taking aliphatic hydrocarbon as solvent, high 1,2-polybutadiene can be easily produced. The absence of a suitable MW regulator may be the reason for being unable to be put into commercial production. By the Fe catalyst, taking phenanthroline as ligand, 1,2-/cis-1,4-binary polybutadiene rubber having good physicomechanical properties and high wet-skid resistance is mainly obtained . However, it is difficult for the Fe catalyst to be used in the commercial production due to the following disadvantages: the ligand is too expensive and cannot be dissolved in an aliphatic solvent; when the polymerization temperature is higher than 30° C., the content of 1,2-structure decreases and the content of cis-1,4-structure increases (Bullets of Polymer (5), 389 (1984); CN 85 1 01897B).